If its a BW 72C, you can change the rear tailstock bearing through the gimble. It sucks, but can be done. Removing the bearing with a slide-hammer puller isn't so bad, its getting the big snap ring off. I don't know how picklejim is greasing his, all the one's I've replaced are sealed units.

As you said earlier you think you have a merc trans,not a borg warner.If the u-joint yoke on the outdrive has a male shaft with external splines it's a BW.If the yoke has a female end with internal splines and a spring on the end it's a merc trans.As for greasing,the aluminum retainer on the end of the output housing has a grease fitting in it at straight up 12 o'clock.You can see this looking in through the bellows. If you remove the retainer ever(which you can only do by removing the engine)be sure to put it back on the same way.There is a hole in the output housing which directs the grease into the bearing.If you need to see a diagram of this go to ishopboating.com.Click on mercruiser diagrams.Then click SHOW MODELS.Scroll down to 330 MIE GM 454 V8 1977-1980 and click on it.Then select transmission assembly sterndrive page 2.This will show you an exploded view of the merc trans.You will see the retainer as part #104.Grease fitting is #108.You must loosen the 6 nuts on the retainer before removing engine.The retainer squeezes the rubber mount #103 tight in the transom housing to serve as your rear mount.